The construction of buildings with prefabricated wall sections is a common practice. Such prefabricated wall sections, which may vary in length, generally are placed horizontally on the floor of the building structure, with the ultimate lower edge of the horizontal wall section placed immediately adjacent the floor location on which it will rest in vertical, upright position. The wall section is lifted and tilted into its desired vertical position, and the section is then secured to the floor.
It has been suggested to provide lifting devices, such as wall jacks, to raise prefabricated wall sections from horizontal to final vertical position in construction of buildings. U.S. Pat. Nos. 2,812,077 and 3,485,386 each disclose a wall jack construction comprising a mechanical hoist having an elongated boom, the lower end of which is pivotally attached by a hinge to the floor of the building construction. Attached to a lower end portion of the boom is a winch with cable. The cable passes about a sheave on the upper end of the boom, and the outer end of the cable is suitably connected to the prefabricated wall adjacent its eventual upper end. The winch is manually operated to pivotally raise the wall section to a vertical position as the boom pivots from vertical to a generally 45 degree angular position during the lifting operation.